Method of vulcanizing an object formed of unvulcanized rubber and rubber product

ABSTRACT

A method of vulcanizing an object formed of unvulcanized rubber, in which the unvulcanized-rubber formed object is vulcanized by pressing and heating by mold means, comprises disposing a fiber sheet member on a surface of the unvulcanized-rubber formed object and vulcanizing the unvulcanized-rubber formed object by the mold means.

TECHNICAL FIELD

This invention relates to a method of vulcanizing an object formed ofunvulcanized rubber and a rubber product produced thereby and, moreparticularly, to a method of vulcanizing an object formed ofunvulcanized rubber and a rubber product produced thereby in which theappearance of the rubber product is improved.

BACKGROUND ART

For example, there is an unvulcanized rubber sheet for a conveyor beltas an unvulcanized-rubber formed object. This unvulcanized rubber sheetfor a conveyor belt is generally vulcanized and molded using avulcanizing belt press. During the process of vulcanizing, due toentrapped air, and due to gas, water and the like generated from theunvulcanized rubber material, clearances are produced between the heatplate of the vulcanizing belt press and the surface of the unvulcanizedrubber sheet pressed by the heat plate, thereby forming depressions onthe obtained conveyor belt surfaces. Therefore, the conveyor beltsurface cannot present a substantially smooth and glossy surface andthere is a problem of having a bad appearance. Particularly in theseyears, a good appearance is desired by users in addition to an excellentproperty.

To solve the above problem, there is conventionally employed a method ofcoating powder of, for example, zinc stearate, talc, mica or the like onthe surface of the unvulcanized rubber sheet. By coating this powder,the entrapped air, and the gas and water (steam) generated from therubber material (inside) between the heat plate and the unvulcanizedrubber sheet at the time of vulcanizing can be exhausted to the outsidevia the clearance formed between the powder and the heat plate.Accordingly, the generation of depressions is restricted and theconveyor belt which improves appearance can be obtained.

However, in the method of coating powder as described above, due to theinsufficient clearance between the unvulcanized rubber sheet and theheat plate, there is a problem that the air and gas cannot be exhaustedeffectively. Since the powder scatters when coated, there is also aproblem of harmful influence on the working environment.

Further as the other method, in Japanese Patent No. 2588209, there isproposed a method for vulcanizing an unvulcanized rubber sheet that hasa sheet-like sponge member adhered to the surface thereof, thesheet-like sponge member having a continuous clearance. Duringvulcanization by a vulcanizing belt press, the rubber being graduallysoftened enters into the clearance of the sponge member and the rubberpushes out the residue air and the like through the continuous clearanceto the outside. Therefore, the generation of the residue air isprevented and depressions is not produced on the surface of the obtainedconveyor belt

However, in the method using the sponge member, the sponge member is soexcellent in expansion that, when adhered to the unvulcanized rubbersheet surface by pressing, the sponge member extends to the longitudinaldirection and reduces with respect to the width direction. Therefore,when the sponge member is adhered to the unvulcanized rubber sheetsurface, it is likely to generate a part that is lack of the spongemember in one or both end portions of the width direction of theunvulcanized rubber sheet surface. Accordingly, it is difficult toadhere the sponge member through the whole surface of the unvulcanizedrubber sheet, and a problem of deteriorating press-processing efficiencyis caused. Further, since the obtained conveyor belt has a structuresuch that the sponge member having a low strength is disposed on thesurface, the abrasion resistance of the surface is deteriorated.

DISCLOSURE OF THE INVENTION

It is an object of the invention to provide a method of vulcanizing anobject formed of unvulcanized rubber and a rubber product obtainedthereby, capable of improving the appearance of the obtained rubberproduct while not harmfully influencing on the work environment, and notdeteriorating the press-processing efficiency or product property.

To achieve the above object, a method of vulcanizing an object formed ofunvulcanized rubber according to the present invention, in which theunvulcanized-rubber formed object is vulcanized by pressing and heatingby mold means, comprises disposing a fiber sheet member on a surface ofthe unvulcanized-rubber formed object and vulcanizing theunvulcanized-rubber formed object by the mold means.

A rubber product according to the present invention comprises avulcanized-rubber formed object and a fiber sheet member embeded in asurface portion thereof.

In accordance with the present invention, since the fiber sheet memberis disposed on a surface of the unvulcanized-rubber formed object to bevulcanized, the residue air, and gas and water generated from theunvulcanized rubber material can be effectively pushed out to theoutside of the mold means by the rubber gradually softening and enteringinto the clearance of the fiber sheet member. Therefore, the surface ofthe obtained rubber product can be prevented from generatingdepressions. Thus, the surface of the obtained rubber product canpresent a substantially smooth and glossy surface and the rubber productcan have a good appearance.

A good working environment can always be maintained, because no powderharmfully affecting on the working environment is used. Since the fibersheet member is not extended or contracted so much as the sponge memberand has a greater strength than that, the press-processing efficiency isprevented from deterioration if the fiber sheet member is pressed ontothe unvulcanized-rubber formed object, and the abrasion resistance ofthe rubber product surface is not lowered.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view showing one example of a method forvulcanizing an unvulcanized-rubber formed object according to theinvention.

FIG. 2 is an enlarged cross-sectional view showing a main part of arubber product obtained by the method in FIG. 1.

FIG. 3 is an explanatory view showing another example of a method forvulcanizing an unvulcanized-rubber formed object according to theinvention.

FIG. 4 is an enlarged cross-sectional view showing a main part ofanother example of the unvulcanized-rubber formed object used in amethod for vulcanizing an unvulcanized-rubber formed object according tothe invention.

FIG. 5 is an enlarged cross-sectional view showing a main part offurther another example of an unvulcanized-rubber formed object used ina method for vulcanizing an unvulcanized-rubber formed object accordingto the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments in accordance with the present invention will bedescribed below with reference to the drawings, using an unvulcanizedrubber sheet for a belt conveyor as an unvulcanized-rubber formedobject.

As shown in FIG. 1, the numeral 1 shows an unvulcanized rubber sheet fora conveyor belt in a long belt-like shape, the numeral 3 long belt typefiber sheet members and the numeral 5 a mold means for molding theunvulcanized rubber sheet 1.

The unvulcanized rubber sheet 1 is wound via an adhesion-preventingliner (not shown) around an unwinding roll 7 which is disposed at theupper flow side of the mold means 5. The fiber sheet members 3 are woundaround upper and lower rolls 9A, 9B, respectively, and stocked there,which are placed between the unwind roll 7 and the mold means 5.

Provided between the rolls 9A, 9B and the mold means 5 are press rollers11A, 11B for pressing the fiber sheet members 3 unwound from the rolls9A, 9B onto the upper and lower surfaces 1 a, 1 b of the unvulcanizedrubber sheet 1. At the lower flow side of the mold means 5, there isdisposed a winding roll 13 for winding a vulcanized rubber sheet 1Y thathas been vulcanized by the mold means 5. The mold means 5 is avulcanizing belt press having upper and lower heat plates 5A, 5B capableof moving up and down to press and heat the unvulcanized rubber sheet 1.

In the vulcanization method of the present invention, first, theunvulcanized rubber sheet 1 is unwound from the unwind roll 7 as shownby an arrow a, and is supplied to the direction shown by an arrow bwhile removing the adhesion-preventing liner (not shown). The fibersheet members 3 are unwound from the rolls 9A, 9B toward the directionshown by arrows c, and pressed and adhered to the upper and lowersurfaces 1 a, 1 b of the unvulcanized rubber sheet 1 by the pressrollers 11A, 11B consecutively.

The unvulcanized rubber sheet 1X provided with the fiber sheet members 3on the both surfaces thereof is then transported between the upper andlower heat plates 5A, 5B. The upper and lower heat plates 5A, 5B,respectively, at the upper and lower waiting positions are moved towardthe unvulcanized rubber sheet 1X to press and heat it for vulcanization.At the time of vulcanizing, air entrapped, and gas, water, etc.,produced from the unvulcanized rubber material remain between the heatplates 5A, 5B and the upper and lower surfaces 1 a, 1 b of theunvulcanized rubber sheet 1.

The unvulcanized rubber sheet 1X pressed and heated between the heatplates 5A, 5B is softened from the central portion toward the peripheralportion. Therefore the softened rubber enters from the central portionside of each of the fiber sheet members 3 into the clearance of thefiber sheet member 3, gradually pushes the air, the gas, and the watertoward the outside thereof and finally excludes them to the outside ofheat plates 5A, 5B.

The heat plates 5A, 5B separate from each other when the vulcanizationis terminated. As a result, as shown in FIG. 2, a conveyor belt (rubberproduct) can be obtained having the fiber sheet members 3 embeded in thesurface portions of the vulcanized rubber sheet (vulcanized-rubberformed object) 1Y. As shown by an arrow d, the vulcanized rubber sheet1Y is transported towards the unwind roll 7 and is wound around theunwind roll 7 as shown by an arrow e. In FIG. 2, the numeral 2 showsreinforce layers embeded in the vulcanized rubber sheet 1Y.

In accordance with the present invention, since the fiber sheet members3 are disposed on the surfaces 1 a, 1 b of the unvulcanized rubber sheet1 to be vulcanized, the residue air, gas, and water can be effectivelyexcluded from the clearance of the fiber sheet members 3 to the outsidethereof. Therefore, no depression appears on the surfaces of theobtained conveyor belt unlike the prior art. Accordingly, the surfacesof the conveyor belt are substantially smooth and glossy, and theappearance of the conveyor belt can be improved.

The deterioration of working environment can be prevented because nopowder which deteriorates the working environment is used. In addition,since the fiber sheet members 3 do not extend much unlike the spongemembers, the press-processing efficiency can not be lowered even if thefiber sheet members 3 are pressed on the unvulcanized rubber sheet 1.The fiber sheet members 3 are greater in strength than the spongemembers, so the resistance of the surfaces of the obtained conveyor beltto abrasion is not deteriorated.

FIG. 3 shows another example of a method for vulcanizing anunvulcanized-rubber formed object according to the present invention. Inthis embodiment, in place of the unvulcanized rubber sheet wound aroundthe unwind roll 7, an unvulcanized rubber sheet 1 pressed out by anextruder 15 is used. This unvulcanized rubber sheet 1 has no reinforcelayers 2 described above. In this way the unvulcanized rubber sheet 1extruded from the extruder 15 may be directly used without winding itaround the unwinding roll 7. The same components as those in FIG. 1 havethe same numerals and the description thereof will be omitted.

FIG. 4 shows another example of the unvulcanized rubber sheet used forthe vulcanizing method of the present invention. This embodimentillustrates a conveyer belt formed into one unit by vulcanization fromtwo unvulcanized rubber sheets 1, end portions 1 e of which areoverlapped in contact with each other. Fiber sheet members 3 arerespectively adhered onto the upper and lower surfaces 1 a, 1 b of theunvulcanized rubber sheets 1 the end portions 1 e of which are broughtinto contact with each other as describe above, and the rubber sheetsare then disposed between the upper and lower heat plates 5A, 5B of thevulcanizing belt press and vulcanized. The obtained conveyor belt havingthe end portions 1 e which have been integrally connected with eachother can exhibit the same effects described above.

FIG. 5 illustrates further another example of the unvulcanized rubbersheet used for the vulcanizing method of the present invention. In thisembodiment, unvulcanized rubber sheets 1L, 1M, 1N, 1P, 1Q are unitarilyjoined by vulcanization to obtain a conveyer belt.

The end portions 1 e of the first unvulcanized rubber sheet 1L andsecond unvulcanized rubber sheet 1M on the lower side butt against eachother. The third unvulcanized rubber sheet 1N embeded with a reinforcelayer 2 is laminated on the unvulcanized rubber sheets 1L, 1M. Thefourth and fifth unvulcanized rubber sheets 1P, 1Q are laminated on thethird unvulcanized rubber sheet 1N. As in the first and secondunvulcanized rubber sheets 1L, 1M, end portions 1 e of the fourth andthe fifth unvulcanized rubber sheets 1P, 1Q, butt against each other.

Fiber sheet members 3 are respectively adhered onto the upper and lowersurfaces 1Ta, 1Tb of the unvulcanized rubber sheet laminate 1T of theabove structure, and the laminate 1T is then placed between the upperand lower heat plates 5A, 5B and vulcanized. The obtained conveyor beltcomprising the rubber sheets 1L, 1M, 1N, 1P, 1Q which have joined intoone unit, can exhibit the same effects described above.

In the present invention, the fiber sheet members 3 may be used havingany of such structures capable of exhausting the residue air or the liketo the outside through the clearance during vulcanization. For example,textile fabrics or knit fabrics in sheet can be preferably used.Nonwoven fabrics may also be used.

For fiber materials of the fiber sheet members 3, any of fiber materialshaving a higher melting point than the vulcanizing temperature may beused. For instance, nylon fiber, polyester fiber, etc., having a meltingpoint of 180° C. or more can be preferably employed.

When textile fabrics or knit fabrics are used for the fiber sheetmembers 3, it is preferable that the mass per unit area thereof may be 5to 30 g/m². If the mass per unit area is less than 5 g/m², thegeneration of crinkling can easily happen when the fiber sheet members 3are adhered onto the unvulcanized rubber sheet 1 by pressing. And sinceit is difficult to effectively exclude the air, etc., depressions caneasily be produced. If the mass per unit area is more than 30 g/m², theconsumption volume of the fiber sheet members 3 is be too exceeded.Since the difference between the color of the fiber sheet members 3embeded in the surface portions and the original color (black ingeneral) of the vulcanized rubber becomes apparent, the appearance isdeteriorated. Moreover, as the adhesion between the fiber sheet members3 and the vulcanized rubber is lowered, the abrasion resistance of thesurfaces of the obtained conveyor belt is lowered.

The thickness of the fiber sheet members 3 using textile fabrics or knitfabrics may be preferably 0.05 to 0.40 mm. If the thickness is out ofthe above range, the same problems as described in case of the mass perunit area are caused.

In case of using nonwoven fabrics for the fiber sheet members 3, it ispreferable that the mass per unit area is 10 to 25 g/m². The thicknessthereof may preferably be 0.05 to 0.20 mm. If the mass per unit area andthe thickness are out of the above ranges, the same problems asdescribed above are caused.

In case of using nonwoven fabrics for conveyor belts, at least in thedirection of the compressive stress acting upon the conveyer belt, it ispreferable that the extension degree at the time of cutting is set to be25% or more and the extension degree under 1/10 of load of the cuttingstrength is set to be 10% or more. These may be set in the same mannerfor the case of other rubber products.

If the extension degree at the time of cutting is less than 25%, or theextension degree under 1/10 of load of the cutting strength is less than10%, the nonwoven fabric, when the compressive stress acts upon the beltin services, is buckled, and crinkling occurs on the conveyor beltsurfaces. Therefore, the belt appearance is deteriorated and the surfaceabrasion resistance is lowered. It is preferable that the upper limitvalue of the extension degree in cutting is 50% and the upper limitvalue of the extension degree under 1/10 of load of the cutting strengthis set to be 20%. If the extension degrees exceed these upper limitvalues, the fiber sheet members extend greatly, thereby deterioratingthe press-processing efficiency as in the sponge member.

In these embodiments, the unvulcanized rubber sheets for a conveyor beltare described as examples of the unvulcanized-rubber formed objects.However, the present invention is not limited thereto and will beadequately used for any of unvulcanized-rubber formed objects, whichhave the same problems as described in the prior art.

EXAMPLE 1

Conveyer belts having a structure shown in FIG. 2 were prepared byvulcanizing unvulcanized rubber sheets for a conveyor belt by thevulcanizing methods 1 to 3 of the present invention, the unvulcanizedrubber sheets having fiber sheet members shown in Table 1. Each fibersheet member was made of Nylon 6, and its mass per unit area was 10 g/m²and the thickness thereof was 0.2 mm.

Conveyer belts having a structure with no fiber sheet member in FIG. 2were also prepared by vulcanizing unvulcanized rubber sheets for aconveyor belt by the conventional vulcanizing method using powder ofzinc stearate (conventional method 1) and by the conventionalvulcanizing method using talc powder (conventional method 2). The powderwas applied for 10 g per 1 m² in each vulcanizing methods.

A conveyer belt having sponge members made of polyurethane (a thicknessof 1 mm) in place of the fiber sheet members in the conveyer belt with astructure of FIG. 2 was also prepared by vulcanizing an unvulcanizedrubber sheet by the conventional vulcanizing method (the conventionalmethod 3) using the sponge members.

In each vulcanizing method, a vulcanizing belt press was used, thevulcanization temperature being 150° C., the vulcanization time periodbeing 30 minutes. Rubber (NR/SBR system rubber) mixed with naturalrubber and styrene-butadiene rubber was used for each of theunvulcanized rubber sheets for a conveyor belt in the vulcanizingmethods, and the width of the rubber sheets was 1 m, the thickness 10 mmand the length 20 m.

Evaluation tests for the generation rate of depressions, surface colorcondition, working environment, press-processing efficiency of the fibersheet members and the sponge members, and surface abrasion resistancewere conducted under the following measuring conditions to the conveyerbelts obtained by the vulcanizing methods. The results were shown inTable 1.

Generation Rate of Depressions

The number of depressions generated on the surfaces of the conveyor beltwhich is obtained by each method is counted and the obtained number isconverted into the generation rate per 10 m².

Surface Color Condition

The test is conducted in accordance with JIS Z8723, “Visual ComparativeEvaluation of Surface Color”. The results are evaluated in three ranksby ◯, Δ, X. ◯ means no problem and a good condition (if any, howeverlittle), Δ means that some problem exists (depressions are clearlyconfirmed), and X means that a great problem exists (the generation ofdepressions are seen in a wide range) and considerable deterioration iscaused.

Working Environment

After producing each conveyor belt by each vulcanizing method, thepolluted state in the whole processes including the equipment isobserved. The results are evaluated in three ranks by ◯, Δ, X. ◯ meansno problem and a good state, Δ means that some problem exists, and Xmeans that a great problem exists and considerable deterioration iscaused.

Press-Processing Efficiency of Fiber Sheet Member and Sponge Member

At the time of producing the conveyor belt, after pressing the fibersheet members and the sponge members onto the surfaces of theunvulcanized rubber sheets by press rollers, the adhesion state of eachfiber sheet member or sponge member on the surface of the sheet obtainedis visually observed. The results are evaluated in three ranks by ◯, Δ,X. ◯ means no problem and a good state, Δ means that some problemexists, and X means that a great problem exists (in a wide range ofunvulcanized rubber sheet surface, portions lack of the fiber sheetmember or the sponge member are generated, or crinkling is observed) andconsiderable deterioration is caused.

Surface Abrasion Resistance

The conveyor belt obtained by each method is cut into a rectangular testpiece having a width of 25 mm and a length of 40 cm. The test piece isbent one million times under the condition of a pulley diameter of 50mm, load of 250 N/overall width, according to Press and Bending FatigueStrength Evaluation (A Method) which is described in JIS L1017. Thesurface of each test piece is then visually observed. The results areevaluated in three ranks by ◯, Δ, X. ◯ means no problem and a good statesuch that only the outer rubber surface of the test piece is abraded andlittle generation of fuzz, rough surface, and detachment of the fibersheet member or of the sponge member can be observed, Δ means someproblem such that fuzz, rough surface and/or detachment of the fibersheet member or of the sponge member can be slightly observed, and Xmeans a great problem such that fuzz, rough surface and/or detachment ofthe fiber sheet member or of the sponge member can be apparentlyobserved and considerable deterioration is caused. TABLE 1 Method 2Method 3 Method 1 of of the of the the Present Present PresentConventional Conventional Conventional invention invention inventionMethod 1 Method 2 Method 3 Fiber Sheet Knit Textile Nonwoven — — —Member fabric fabric fabric Generation Rate 0 0 0 1.3 1.1 0 ofDepressions (number/10 m²) Surface Color ◯ ◯ ◯ ◯ Δ ◯ Condition Working ◯◯ ◯ Δ Δ ◯ Environment Press- ◯ ◯ ◯ — — X Processing Efficiency Surface ◯◯ ◯ ◯ ◯ Δ Abrasion Resistance

As shown in Table 1, the vulcanizing methods of the present inventioncan obtain conveyer belts (rubber products) having a good appearance,without deteriorating the working environment, the press-processingefficiency of the fiber sheet member and the surface abrasionresistance.

EXAMPLE 2

Fiber sheet members were prepared each having the mass per unit shown inTable 2, the fiber sheet members being made of the same knit fabric asused in the example 1. Unvulcanized rubber sheets with these fiber sheetmembers were vulcanized by vulcanizing methods using the fiber sheetmembers (Methods A to E), and conveyor belts having a composition asshown in FIG. 2 were obtained. Other conditions were the same as in theexample 1.

Evaluation tests for the generation rate of depressions, surface colorcondition, working environment, press-processing efficiency of the fibersheet members and the sponge members, and surface abrasion resistancewere conducted under the same measuring conditions as shown in theexample 1 to the conveyer belts obtained by the vulcanizing methods. Theresults were shown in Table 2. TABLE 2 Vulcanizing VulcanizingVulcanizing Vulcanizing Vulcanizing Method A Method B Method C Method DMethod E Unit Mass 4   5 10 30 35 (g/m²) Generation Rate 0.2 0  0  0  0of Depressions (number/10 cm²) Surface Color ◯ ◯ ◯ ◯ Δ˜X ConditionWorking ◯ ◯ ◯ ◯ ◯ Environment Press-Processing X ◯ ◯ ◯ ◯ Efficiency(crinkling) Surface Abrasion ◯ ◯ ◯ ◯ Δ˜X Resistance

As shown in Table 2, it is understood that the mass per unit area of thefiber sheet members composed of knit-fabric is preferably 5 to 30 g/m².

EXAMPLE 3

Fiber sheet members were prepared each having the mass per unit shown inTable 3, the fiber sheet members being made of the same nonwoven fabricas used in the example 1. Each nonwoven fabric was arranged such thatthe extension degree at the time of cutting was 35%, and the extensiondegree under 1/10 of load of the cutting strength was 14%. Unvulcanizedrubber sheets with these fiber sheet members were vulcanized byvulcanizing methods using the fiber sheet members (Methods F to J), andconveyor belts having a composition as shown in FIG. 2 were obtained.Other conditions were the same as in the example 1.

Evaluation tests for the generation rate of depressions, surface colorcondition, working environment, press-processing efficiency of the fibersheet members and the sponge members, and surface abrasion resistancewere conducted under the same measuring conditions as shown in theexample 1 to the conveyer belts obtained by the vulcanizing methods. Theresults were shown in Table 3. TABLE 3 Vulcanizing VulcanizingVulcanizing Vulcanizing Vulcanizing Method F Method G Method H Method IMethod J Unit Mass 7 10 15 25 30 (g/m²) Generation Rate 0.2 0 0 0 0 ofDepressions (number/10 cm²) Surface Color ◯ ◯ ◯ ◯ X Condition Working ◯◯ ◯ ◯ ◯ Environment Press-Processing X ◯ ◯ ◯ ◯ Efficiency (crinkling)Surface Abrasion ◯ ◯ ◯ ◯ Δ Resistance

As shown in Table 3, it is understood that the mass per unit area of thefiber sheet members made of nonwoven fabric is preferably 10 to 25 g/m².

As described above, according to the method of the present invention forvulcanizing an object formed of unvulcanized rubber, since the fibersheet member is disposed on the surface of the unvulcanized-formedobject to be vulcanized, the residue air and the like can be excludedfrom the clearance of the fiber sheet member to the outside duringvulcanization. Therefore, depressions produced on the surface of theobtained rubber produce can be prevented. Accordingly, the surface ofthe rubber product obtained can be substantially smooth and glossy andit has a good appearance.

Since powder harmfully affecting on the working environment is not used,a good working environment can be maintained. In addition, the fibersheet member has a higher strength than the sponge member, and is noteasily extended or contracted, so the processing efficiency at the timeof pressing and surface abrasion resistance can not be lowered.

POSSIBILITY OF INDUSTRIAL USE

The vulcanizing method of the present invention, which has excellenteffects described above, is very useful to vulcanize unvulcanied-rubberformed objects in the vulcanizing process when rubber products such asconveyor belts are produced.

1. A method of vulcanizing an object formed of unvulcanized rubber inwhich the unvulcanized-rubber formed object is vulcanized by pressingand heating by mold means, comprising; disposing a fiber sheet member ona surface of said unvulcanized-rubber formed object; and vulcanizing theunvulcanized-rubber formed object by said mold means.
 2. A method ofvulcanizing an object formed of unvulcanized rubber according to claim1, wherein said fiber sheet member is selected from textile fabric ornonwoven fabric.
 3. A method of vulcanizing an object formed ofunvulcanized rubber according to claim 1 or 2, wherein said fiber sheetmember is formed of fiber material having a melting point higher thanvulcanizing temperature.
 4. A method of vulcanizing an object formed ofunvulcanized rubber according to claim 3, wherein the fiber material ofsaid fiber sheet member has a melting point equal to 180° C. or higher.5. A method of vulcanizing an object formed of unvulcanized rubberaccording to claim 2, wherein said fiber sheet member comprises atextile fabric, and the mass per unit area of the fiber sheet member is5 to 30 g/m².
 6. A method of vulcanizing an object formed ofunvulcanized rubber according to claim 5, wherein the thickness of saidfiber sheet member is 0.05 to 0.40 mm.
 7. A method of vulcanizing anobject formed of unvulcanized rubber according to claim 2, wherein saidfiber sheet member comprises a nonwoven fabric, and the mass per unitarea of the fiber sheet member is 10 to 25 g/m².
 8. A method ofvulcanizing an object formed of unvulcanized rubber according to claim7, wherein the thickness of said fiber sheet member is 0.05 to 0.20 mm.9. A method of vulcanizing an object formed of unvulcanized rubberaccording to any one of claims 1, 2 and 5 to 8, wherein said fiber sheetmember is disposed on surfaces of the unvulcanized-rubber formed objectsend portions of which come into contact with each other.
 10. A method ofvulcanizing an object formed of unvulcanized rubber according to any oneof claims 1, 2 and 5 to 8, wherein said fiber sheet member is pressed onthe surface of said unvulcanized-rubber formed object.
 11. A method ofvulcanizing an object formed of unvulcanized rubber according to any oneof claims 1, 2 and 5 to 8, wherein said mold means is a vulcanizing beltpress having upper and lower heat plates for pressing and heating.
 12. Arubber product comprising a vulcanized-rubber formed object and a fibersheet member embeded in a surface portion thereof.